I understand the warmth part (I sweat like a pig in my Judo gi) but how does it help with control?

I guess your sweatiness isn't as much of a factor as it is without a gi? But don't the disadvantages outweight the advantages?

When two guys go no gi, things are very slick. Stuff tends to happen quicker, and explosive wrestler types tend to do better as they can abruptly power out of some locks and hold downs. With a gi, there is less slippage, and people are less likely to be able to just jerk out of a hold. This tends to make the groundfighting a bit slower and more technical. It rewards the technician a bit more than the raw, explosive athlete.

No-gi vs. no-gi is very quick. Gi vs. gi is a bit slower. Grip becomes more important, collar chokes come into play, hold downs are a bit easier. Throws can be a bit more technical and grip-based, while meat-on-meat single and double legs, fireman's carries, suplex, etc., are still available.

In gi vs. no-gi, it's a bit of a compromise between the two. It will slow things down a little, especially once on the ground, but it seems very debatable whether it's really worth trying to me. If you can't collar choke your opponent, but he can collar choke you, this sucks. If you can't use grip-based throws, but he can, then this sucks. Maybe if you're just planning on tripping him, it could help you on top if you get a hold down. Or if you're planning on just pulling guard and fighting from the bottom, it could be helpful.

But against an aggressive, momentum-based fighter like Silva, it seems like something of a bad idea to me.